1. Field of the Invention
The present invention relates to a method for chemically treating a glass surface to prevent "whitening" thereof and, more particularly, to a glass plate used for an integrated circuit in electronics, optical apparatus or building structures.
2. Description of the Prior Art
It is known that glass surfaces and, more particularly, the surface of glass whose material contains sodium, potassium or other alkali metals, i.e., alkali glass, becomes white or smoked when exposed to moist air after manufacturing of the glass. This phenomenon is hereinafter referred to as "whitening." When such a glass plate is used for an integrated circuit, it is necessary that the surface be extremely smooth and free of impurities and imperfections. Whitening shows that the surface of the glass is not extremely smooth and reduces the yield of the product in the processing that follows. Accordingly, the phenomenon must be severely inhibited. Furthermore, the prevention of whitening is widely desired in the field of glass incorporated within precision optical instrument or apparatus as well as with a building construction material because the change in color is objectionable.
It has been considered that the whitening that evloves on a glass surface is due to moisture in the atmosphere. To inhibit whitening, treatment with various chemicals and treatment with heat have been attempted. For example, organic materials or moisture on a glass surface may be removed with a neutral detergent or with isopropanol or freon, respectively. While these methods temporarily remove impurities and moisture existing on a glass surface, they cannot be removed permanently. Furthermore, the surface of the glass absorbs moisture again in the air to generate the whitening phenomenon as a result of a slight deviation of temperature. Glass treated in accordance with the above methods has only a limited utility since it causes a peeling phenomenon of a coating thereon, a chemical change on its surface and the like.